Counter chronograph



NM. 20, 1951 w. A. HIGINBOTHAM ET AL 2,575,759

COUNTER CHRONOGRAPH Filed Feb. '7, 1949 2 HEET l Gmsfiazz? Frequenc Impulse Source Amplifier Anal Scale)" Pulse Sharper I VilZiam A.Higin5ofi7zam M B'ayce a McDaniel BY K g MAJ/M NW1 2(0) 31951 w. A. HIGINBOTHAM ET AL 5 9 COUNTER CHRONOGRAPH 2 SHEETSSHEET 2 Filed Feb. '7, 1949 Patented Nov. 20, 1951 COUNTER CHRONOGRAPH William A. Higinbotham, Upton, and Boyce D. McDaniel, Ithaca, N. Y., assignors to the United States of America as represented by the United States Atomic Energy Commission Application February 7, 1949, Serial No. 75,048

1 Claim. 1

The present invention relates to electronic chronographs and more particularly to control means operable to permit activation or deactivation of such chronographs in a predetermined manner.

Electronic timing circuits or chronographs as known heretofore have generally included a source of constant frequency impulses, an electronic counting circuit and associating these components a control circuit which, in response to a predetermined externally derived signal. permits said constant frequency impulses to reach the counter circuit, and in response to a second externally derived signal, to stop the counting of said impulses. Such systems are disclosed for example in Cook, U. S. Patent 2,332,300 and in the copending U. S. patent application of Sands, Serial No. 606,406, filed July 21, 1945.

It is an object of the present invention to provide simplified, quick acting, control means for counter chronograph systems.

It is a further object of the present invention to provide control means for electronic counter chronographs which automatically resets the systern for successive timing operations.

Still another object of the present invention is toprovide a simply constructed precise electronic chronograph for measurin time intervals of the order of hundreds of microseconds.

Other objects and advantages of the present invention will be apparent from the following specification taken in connection with the drawings made a part hereof, and the description of a presently preferred embodiment.

In the drawings:

Fig. 1 is a functional diagram in block form of a counter chronograph constructed in accordance with the principles of the present invention.

Fig. 2 is a schematic circuit diagram of a chronograph showing details of the invention.

Referring to Fig. 1, the electronic chronograph of the present invention is seen to comprise a source 5 of constant frequency impulses associated through a controlled pulse shaper B with a frequency dividing circuit or scaler I.

Pulse shaper 6 is controlled in accordance with the condition of balance of a two mode circuit 8 and the reflection of said condition of balance in the control device 9. Means for introducing an initiating and terminating signal are designated by reference numerals 3 and 4 respectivel and are shown associated with two mode circuit 8.

Turning now to Fig. 2, the source of constant frequency impulses is not shown as such but is indicated by input terminal 30. Such impulses are fed through condenser 3I and resistor 32 to the control grid of pentode type tube I0. Tube I0 and tube II are associated in a well known trigger circuit manner and together form the pulse shaper 6 of Fig. 1. More particularly, cathodes 39 and 4I and suppressor grids 43 and 44 are connected together and are connected to ground 50 through resistor 42. Screen grids 46 and 4'! are connected directly to a source of positive potential indicated by conductor 40. Anodes 48 and 5| are connected to potential conductor 40 through resistors 49 and 52, respectively; furthermore, anode 48 of tube I0 is coupled to grid 58 of tube II through the network including resistor 54 and capacitor 56. Grid 58 is also connected to ground through fixed resistor 51 and variable resistor 55. Likewise, input grid 33 of tube I0 is connected to ground and conductor 40 through the voltage divider, including resistors 36, 31, 38 and 34. With this arrangement grid 33 is maintained at a potential which will keep tube I0 cut ofi except for some portion of the oscillatory input to terminal 30. (It should be noted here that in this particular circuit, grid 33 never becomes positive with respect to cathode 39 as grid current is not drawn even when tub I0 is conducting. It should also be noted that tube II is normally conducting.) Control grid 33 will rise with this input to a critical value (fixed by the circuit constants) at which tube I0 begins to conduct and tube I I is cut off (when proper conditions exist), which state continues until the input impulse falls below the starting voltage. As a result of such action, the output at anode 5i of tube I I takes the form of a square wave of known amplitude which is operative to activate sealer circuits indicated by numerals I03, I04 and I 05 and neon indicators I06, I0! and I08. The rectangular voltage wave generated at the plate of tube II is fed directly to the scaler unit I03 which feeds scaler units I04 etc. I05. Sealer unit I05 may be of the type shown in Patent 2,442,403 and can be employed to drive tube I06 which operates a mechanical counter I 07.

The passage of the constant frequency impulses through the pulse shaper circuit, including tubes I0 and II, to the counter circuits is controlled in accordance with the principles of the present invention by varying the potential of grid 58. To this end, triode type tube I2 is provided and associated with tube II by having its cathode I9 directly connected to grid 58 of tube II. Anode I8 of tube I2 is directly connected to conductor 40 and grid 13 is connected to ground through the alternative paths consisting of resistor I7 and switch 88 which is in the normally open position. The connection of tube I2 is termed for the purpose of the present specification as that of a cathode follower.

Conductivity or non-conductivity of tube I2, in addition to being dependent on the condition of switch 80 in a manner which will be apparent hereafter, is also dependent upon the condition of balance of the two mode system including tubes I4 and I5. These tubes are connected in the manner known as a trigger circuit, i. e., in which they operate in a stable mode of balance, or upon the application of a suitable signal, in an unstable mode of balance for a period dependent upon the network constants. More particularly, cathodes 86 and 81 are connected together and to ground through resistor 88. Control grid 8| of tube I4 is connected to ground through resistor 82 and control grid 89 receives its biasing potential through the connection to conductor 48 through resistor 90. Anode I is connected to conductor 40 through resistors II and I2 and anode 84 is connected to conductor 40 through resistor 92. The respective grids and anodes are cross connected in the usual manner, grid 89 being connected to the junction of resistors II and I2 through condenser BI, and grid BI being connected to anode 84 through the network including resistor 83 and condenser 93.

Anode I8 is connected through the network including condenser I6 and resistor I4 to the control grid I3 of tube I2 and is also connected directly to anode 69 of tube I3, which serves as the input for the starting signal for the chronograph. An input terminal 59 is provided and connected through condenser GI to control grid 62. Resistor 83 is connected between said grid 62 and ground. Cathode 64 is connected at the junction point of resistors 66 and 61 which are arranged in series between conductor 40 and ground. By-pass condenser 68 is provided in shunt with resistor 81.

An input is also provided for the stopping signal for the chronograph in the form of tube I6 and the terminal 60 associated through condenser 94 with the control grid 96 of said tube. Resistor IN is connected between grid 96 and ground. Anode I82 is connected directly to anode 84 of tube I and cathode 91 is connected to the junction point of resistors 98 and 99 arranged in series between conductor 40 and ground. By-pass condenser IOD is provided in shunt with resistor 99.

Turning now to the operation of the circuit hereinabove described, the cyclically varying time base impulses applied between terminal and ground causes grid 33 to be raised sufliciently to allow tube In to conduct and tube I I to be cut off when the potential of grid 58 is at a proper level in accordance with the non-conductive condition of tube I2. Tube II) will continue to conduct until the oscillatory input voltage falls below the critical starting value at which time the pulse shaping circuit, including tubes I0 and II, returns to its stable state. Thus a square wave output may be accomplished at anode 5| of tube II, which output is fed through conductor I! to the counter circuit.

It is a feature of the present invention to vary the potential of grid 58 rapidly at predetermined times by controlling conduction of tube I2. Thus, with switch 80 in the open position, tube I2 is normally conducting and as a consequence of the direct connection of cathode I9 thereof to grid 58 of tube II, cathodes 39 and M are maintained at a potential, relative to grid 33, such that tube III no longer conducts on any part of the oscil- 4 latory input. Consequently the current in tube II is not interrupted and no pulses appear at anode 5I.

This condition is maintained until a predetermined positive signal is applied to terminal 59 and hence to grid 62 of tube I3. This signal, externally derived, is indicative of the beginning of the interval to be timed. Upon the appearance of the signal at grid 62 the potential of anode 69 is reduced and the negative signal thus produced is applied to control grid I3 and efiects the cessation of conduction in tube I2. The cessation of conduction in tube I2 decreases the potential of cathode I9 and thereby the potential of grid 58 of tube II. This reduces the amount of current flowing through tube II and thereby lowers the potential of cathodes 39 and II, relative to grid 33. Tube II) will now conduct on some portion of the oscillatory input and tube II is in condition to be cut off when the potential of grid 58 is lowered further by the action of anode 48 when tube I0 begins to conduct. Thus, periodic pulsations appear at grid 58 of tube II to effect operation of the counting circuits.

The same negative signal appearing at anode 69 is applied to grid 89 of tube I5, which reduces conduction in that tube, thereb increasing the potential at anode 84. Regenerative efiects lower the potential at grid 89 of tube I5 until that tube is cut on and tube I4 is conducting. As a consequence of conduction in tube I4, grid I3 of tube I2 is held at a potential at which said tube I2 is prevented from conducting.

At the end of the interval being timed a sec ond externally derived positive signal is applied to terminal 60 and through condenser 94 to grid 98 of tube I6. This signal raises grid 96 and thus lowers the potential at anode I82 and the resultant negative signal is applied to grid M of tube I4 efiecting cut off of the same and the immediate return of the trigger circuit to its original stable state. concomitantly, the sudden rise in potential of anode 89 is applied to grid I3 of tube I2 and said tube l2 again conducts whereby cathodes 39 and 4| are maintained at such a potential that tube III is prevented from conducting.

It should be noted that in the embodiment described the A. C. coupling constants, resistor 90 and condenser 9|, of the trigger circuit, made up of tubes I4 and I5, are chosen so that the said circuit automatically returns from the unstable to the stable state after a predetermined time even if no terminating signal is applied to terminal This predetermined time is fixed in excess of the time interval under observation. Thus the system is automatically reset after a timing operation and no indicating or like components, as well as manual resetting means are required to show the operative or inoperative condition obtaining in the system. It is clear that other benefits of the invention may be enjoyed independently of this feature.

The operation of the counting circuits is not described in detail herein as any well known circuits may be employed with the end result that the number of pulses (from the source associated with the terminal 30) between the initiating and terminating signals applied respectively to terminals 59 and 68 are counted and indicated, and the time interval between said signal determined. It is apparent that when switch is closed, the operation of the counting circuits is carried out independently of externally derived timing pulses and thus may be manually activated or deactivated. I

It should be noted that a particular advantage of the present system accrues from the manner in which the operation of tube l l to pass activating signals is controlled to within fractions of a microsecond. It should be noted further the phase relationship of the shaped output pulses (activating signals) to the sine wave input pulses may be controlled independently of those circuit constants which control the timing interval.

It will thus be seen that what has been described herein is a simple chronograph system of high precision, featuring, in addition, automatic resetting characteristics. Many variations in the arrangement of the system, the type of trigger circuits or in the networks described will now be apparent to one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claim.

What is claimed is:

A timing circuit comprising a one-shot multivibrator, an electronic counting circuit, a clamping circuit, and means for deactivating the clamping circuit for an interval determined by the successive occurrence of two input pulses, said one shot multivibrator comprising first and second thermionic tubes each having at least a cathode, a control grid and an anode, means for impressing wave energy of selected frequency on the grid of the first thermionic tube, said clamping tube having at least a cathode, control grid and anode, a load resistor connected to the cathode of the clamping tube and a connection between the clamping tube cathode and the one shot multivibrator second the mionic tube control grid, said means for deactivating the clamping circuit comprising a univibrator having first and second univibrator tubes each having at least for impressing a second input pulse on the univibrator to efiect a state of lowered positive potential on the univibrator first tube anode to depress the control grid potential of the clamping tube to thereby open circuit the same and activate the one shot multivibrator to generate rectangular pulses in synchronism with the impressed input wave energy, and means coupling the rectangular pulses to the said electronic counting circuit.

WIILIAM A. HIGINBOTHAM. BOYCE D. MCDANIEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS.

Number Name Date 2,332,300 Cool; Oct. 19,1943 2,442,403 Flory et a1. June 1, 1948 2,512,330 Hendrich June 20, 1&50

OTHER REFERENCES Abstract, 715,443, published July 19, 1949, filed Dec. 11, 1946. 

